Dehydrogenation of a cycloolefinic hydrocarbon containing a geminal carbon atom



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Patented Dec. 1, 1953 DEHYDROGENATION OF A CYCLOOLEFINIC HYDROCARBON CONTAINING A GEMINAL CARBON ATOM Herman Pines and Vladimir N. Ipatiefl, Chicago,

Ill., assignors to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware No Drawing. Application April 28, 1950,

Serial No. 158,911 7 12 Claims. (01.260-668) This invention relates to the conversion 01' cyclo-olefinic hydrocarbons into aromatic hydrocarbons. More particularly, the process relates to the conversion of a cyclohexene hydrocarbon containing a geminal carbon atom into an aromatic hydrocarbon containing one more substituted nuclear carbon atoms than present in said cyclohexene hydrocarbon.

By a cyclohexene hydrocarbon containing a geminal carbon atom, we mean a cyclohexene hydrocarbon having at least one carbon atom in the ring with two substituent hydrocarbon groups attached thereto. Thus, a cyclohexene hydrocarbon containing a geminal carbon atom comprises, for example, a 1,1,3-trialkyl-:c-cyclohexene as 1,1,3-trimethyl-a:-cyclohexene, in which a: indicates the variable position of the double bond although it is preferably present in the cyclohexene ring rather than in an unsaturated side chain.

This invention is particularly applicable to the conversion of alkyl cyclohexene hydrocarbons having at least one carbon atom in the ring with two alkyl groups attached thereto and more particularly to polymethylcyclohexenes of this structure. That is, such cyclohexene hydrocarbons have a geminal carbon atom and also have at least one and not more than five nuclear carbon atoms combined with hydrocarbon group substituents. comprise methyl groups but it is understood that the invention is also applicable to the treatment of gem cyclohexene hydrocarbons in which the The substituent groups usually 5* substituent groups are other alkyl groups such as ethyl, propyl, butyl etc., or are cycloalkyl groups, such as cyclopentyl, cyclohexyl, etc., aryl, such as phenyl, etc., or are mixtures of said substituents.

One embodiment of this invention relates to a process for producing an alkyl aromatic hydrocarbon which comprises dehydrogenating a bon atom and also having at least one and not 1 more than five nuclear carbon atoms combined with hydrocarbon group substituents in the presence of an acidic material to produce an alkyl aromatic hydrocarbon having one more substituted carbon atoms than present in said cyclohexene hydrocarbon and recovering said alkyl aromatic hydrocarbon.

A further embodiment of this invention relates to a process for producing an alkyl aromatic hydrocarbon which comprises dehydrogenating a cyclohexene hydrocarbon having a geminal carbon atom and also having at least one and not more than five nuclear carbon atoms combined with hydrocarbon group substituents in the presence of an alkyl halide to produce an alkyl aromatic hydrocarbon having one more substituted carbon atoms than present in said cyclohexene hydrocarbon and recovering said alkyl aromatic hydrocarbon.

We have found that when an alkyl cyclohexene containing a geminal carbon atom such as 1,1,3- trimethyl-x-cyclohexene is passed over a dehydrogenation catalyst such as chromia-alumina, dehydrogenation and also demethylation reactions occur to produce an aromatic hydrocarbon having one less alkyl group than present in the charged alkyl cyclohexene containing a geminal carbon atom. Thus 1,1,3 trimethyl-x-cyclohexene when contacted with chromia-alumina catalyst at 500 C. yielded substantial amounts of metaxylene together with methane and hydrogen as indicated by the following equation:

In the process of the present invention, we have found that demethylation can be avoided substantially during dehydrogenation by having present in the reaction mixture an acidic material or acid-producing compound which is added either continuously or intermittently to the alkyl cyclohexene being charged to dehydrogenation. Such acid-producing compounds include particularly alkyl halides, hydrogen halides, etc. For example, when 5% by volume of butyl chloride was added to 1,1,3-trimethyl-a:-cyclohexene and this solution was passed over chromia-alumina catalyst at a temperature of 500 0., the product obtained consisted of 1,2,4-trimethyl-benzene and not of meta-xylene, which might form as a result of combined dehydrogenation and demethylation. Thus the aromatic product of this process, namely, 1,2,4-trimethylbenzene, has three substituted nuclear carbon atoms whereas the 1,1,3-trimethyl--:rcyclohexenev has only two substituted carbon atoms as one of these substituted carbon atoms is a geminal carbon atom.

The catalysts preferred for this process comprise chromia or chromia supported on alumina and the like. In the presence of dehydrogenation catalysts such as a1umina, -on othen satisfactory carriers composited with a; compound. andpar-- ticularly an oxide of an element in the left-hand columns of groups IV, V, and VI of the periodic table or mixtures thereof and more particularly alumina-chromia or alumina-molybdenum, oxide are also employed within the scope ofthe present invention but not necessarily under; the: same-con;-

ditions of treatment and not necessarily with:

equivalent results. These catalysts which donot contain platinum are generally utilized at a temperature of from about 400 to about 550? C. Thosecatalysts' that contain platinumrequire lower temperatures; such as 250to 425 C. Alkyl aromatic hydrocarbons" formed by this process are useful as solvents, as intermediates inorganic synthesis as in the production of dyes, medicinals, insecticides; etc. Some of'the' lower boiling polyalkylated aromatic hydrocarbons have high anti-knock qualities and are accordingly va-luable-componentsof gasolines.

Althoughthe acid-producing material or acidic material employed in this process to promote isomerization during dehydrogenation may be added continuously; or intermittently together with thehydrocarbon charging stock; a dehydrogenation catalyst may-alsobeprepared in which a stable acid-acting compound is present therein as well as a material which promotes dehydrogenation. Thus; the presence of small amounts or silica-alumina mixed .with a dehydrogenation catalyst will promote both dehydrogenation and isomerization. Also the addition of a small amount of hydrofluoric or hydrochlbricacid; to alumina forms an acid-type catalyst suitable for promoting the dehydrogenation and isomerization reactions of this process. The invention isillustrated further by the following examples but it is to be understood that thebroad scope of theinvention is not limited, thereto.

Example I 1,l, 3 -trimethyl-, a: cyclohexene 24.5grams),

which was obtained by the dehydration of 3,3,5- trimethylcyclohexanol by passing it over activated alumina at 400 C., waspassed over a chromiaalumina catalyst at 500 C. and at an hourly liquid space velocity of 0.4. The liquid product resulting from the dehydrogenation was m-xylene. The yield was. almost quantitative;

Example I I combined with hydrocarbon group substituents and having at least one replaceable nuclear hydrogen atom in the presence of a dehydrogenation catalyst selected from the group consistingof platinum, and" an oxide ofian element in the left hand columns of groups IV, V, and VI of the periodic table and mixtures thereof and an acidic material selected from the group consisting of. alkylrhalideahydrogen halides, and silica-3 aluminaa to. produce an alkylaromatic hydrocarbom having, one; more substituted carbon atom than present, in saidcyclohexene and recovering said alkylaromatic hydrocarbon.

2. A process for producing an alkylaromatic hydrocarbon which comprises dehydrogenating a cyclohexene hydrocarbon having a geminal carbon atom and also having at least one and not more than five nuclear carbon atoms combined with hydrocarbon group-substituents in the presence of a dehydrogenation catalystuselectedirom thev groupconsisting of platinum and. an oxide of an element inthe, left hand columns. of groups IV,.V, and" VI of. the periodic table and. mixtures thereof, and an acidic material selected frornthe. group consisting of alkyl'halides, hydrogen halides, and silica-alumina, to produce an alkylaromatic hydrocarbon having one. more substituted carbon atom than presentin said'cyclohexene hydrocarbon and recovering said alkyl'aromatic hydrocarbon.

' 3.-A process for producing an alkylaromatic. hydrocarbon which comprises dehydrogenating. a cyclohexene hydrocarbon having a geminal carbon; atom and also having at least one and not. more" than five nuclear carbon atoms combined. with hydrocarbon group substituents in the pres.- ence of a dehydrogenation catalyst selected from thegroup, consisting of platinum and an oxide. of an element-in the-left hand columns of groups, IV, V,.and VI of the periodic table and mixtures thereof; and'an alkyl halide'to produce an alkylaromatic hydrocarbon having one. more substituted carbon atom than present in said cyclohexene' hydrocarbon and recovering said alkylaromatic hydrocarbon.

4. A process for producing an alkyl aromatic. hydrocarbon which comprises dehydrogenating. in the presence of a chromia-alumina catalyst at a. temperature of from about 400 to about 550 C. a cyclohexene hydrocarbon having avgeminal carbon atom and having at least one and not" more than five nuclear carbon atoms combined with hydrocarbon group substituentsin the presence ofan acidic material selected from the group. consisting of alkyl halides,, hydrogen halides, and silica-aluminato produce an alkyl aromatic hydrocarbon having one more substituted carbon atoms than present in said cyclohexene hydrocargon and'recovering; said alkyl aromatic hydrocaron. i

5. A process for producing an alkyl aromatic hydrocarbon which comprises dehydrogenating in the presence of a chromia-alumina catalyst at a temperature-of from about 400 toabout 550"" C'. a cyclohexene hydrocarbon having a geminalcarbon atom and having at least one and not more than five nuclear carbonatoms combined with hydrocarbon group substituents" the presence of a hydrogen halide to produce an alkyl aromatic hydrocarbon having one more substituted carbon atoms than present in said cyclohexene hydrocar- Eon. and recovering said alkyl aromatic hydrocar- 6;. A. process; for. producing: an. alkyl aromatic hydrocarbon! which: comprises dehydrogenating" in the presence of a chromia-alumina catalyst at a temperature of from about 400 to about 550 C. a cyclohexene hydrocarbon having a geminal carbon atom and having at least one and not more than five nuclear carbon atoms combined with hydrocarbon group substituents in the presence of an alkyl halide to produce an alkyl aromatic hydrocarbon having one more substituted carbon atoms than present in said cyclohexene hydrocarbon and recovering said alkyl aromatic hydrocarbon.

7. A process for producing an alkyl aromatic hydrocarbon which comprises dehydrogenating in the presence of a chromia-alumina catalyst at a temperature of from about 400 to about 550 C. a cyclohexene hydrocarbon having a geminal carbon atom and having at least one and not more than five nuclear carbon atoms combined with hydrocarbon group substituents in the presence of an alkyl chloride to produce an alkyl aromatic hydrocarbon having one more substituted carbon atoms than present in said cyclohexene hydrocarbon and recovering said alkyl aromatic hydrocarbon.

8. A process for preparing 1,2,4-trimethylbenzene which comprises catalytically dehydrogenating 1,1,3-trimethyl-:x:-cyclohexene in the presence of a dehydrogenation catalyst selected from the group consisting of platinum, and an oxide of an element in the left hand columns of groups IV, V, and VI of the periodic table and mixtures thereof and an alkyl halide to produce 1,2,4-trimethylbenzene and recovering 1,2,4-trimethylbenzene.

9. A process for preparing 1,2,4-trimethylbenzene which comprises dehydrogenating 1,1,3-trimethyl-w-cyclohexene in the presence of a chromia-alumina catalyst and of an alkyl halide at a temperature of from about 400 to about 550 C. to produce 1,2,4-trimethylbenzene and recovering said 1,2,4-trimethylbenzene.

10. A process for preparing 1,2,4-trimethylbenzene which comprises dehydrogenating 1,1,3-trimethyl-r-cyclohexene in the presence of a chromia-alumina catalyst and of an alkyl chloride at a temperature of from about 400 to about 550 C. to produce 1,2,4-trimethylbenzene and recovering said 1,2,4-trimethy1benzene.

11. A process for preparing 1,2,4-trimethylbenzene which comprises dehydrogenating 1,1,3-trimethyl-m-cyclohexene in the presence of a chromia-alumina catalyst and of a butyl chloride at a temperature of from about 400 to about 550 C. to produce 1,2,4-trimethylbenzene and recovering said 1,2,4-trimethylbenzene.

12. A process for preparing 1,2,4-tr1methylbenzene which comprises dehydrogenating 1,1,3-trimethyl-r-cyclohexene in the presence of a chromia-alumina catalyst and of sec-butyl chloride at a temperature of from about 400 to about 550 C. to produce ,2,4-trimethylbenzene and recovering said 1,2,4-trimethylbenzene.

HERMAN PINES. VLADIMIR N. IPATIEFF.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,431,755 Ipatiefi et a1. Dec. 2, 1947 2,435,443 Ipatiefif et al. Feb. 3, 1943 OTHER REFERENCES Linstead et a1.: Dehydrogenation Part II. The Elimination and Migration of Methyl Group. Jour. Chem. Soc. (1940), pages 1127-34 (8 pages. Pages 1127 and 1129 are especially relied upon). 

1. A PROCESS FOR PRODUCING AN ALKYLAROMATIC HYDROCARBON WHICH COMPRISES DEHYDRAGENATING A CYCLOHEXENE HAVING A GEMINAL CARBON ATOM AND ALSO HAVING AT LEAST ONE NUCLEAR CARBON ATOM COMBINED WITH HYDROCARBON GROUP SUBSTITUENTS AND HAVING AT LEAST ONE REPLACEABLE NUCLEAR HYDROGEN ATOM IN THE PRESENCE OF A DEHYDROGENATING CATALYST SELECTED FROM THE GROUP CONSISTING OF PLATINUM, AND AN OXIDE OF AN ELEMENT IN THE LEFT HAND COLUMNS OF GROUPS IV, V, AND VI OF THE PERIODIC TABLE AND MIXTURES THEREOF AND AN ACIDIC MATERIAL SELECTED FROM THE GROUP CONSISTING OF ALKYL HALIDES, HYDROGEN HALIDES, AND SILICA-3 ALUMINA TO PRODUCE AN ALKYLAROMATIC HYDROCARBON HAVING ONE MORE SUBSTITUTED CARBON ATOM THAN PRESENT IN SAID CYCLOHEXENE AND RECOVERING SAID ALKYLAROMATIC HYDROCARBON. 